1. Field of the Invention
The present invention relates to a heat exchanger for heating a passenger compartment of a vehicle by carrying out heat exchange between air and hot water (engine coolant), to which an electric heat emitter is attached.
2. Description of Related Art
A heating heat exchanger to which an electric heat emitter is attached is disclosed in Japanese Patent Publication No. 63-20341. According to this heat exchanger, the electric heat emitter is integrated with the heat exchanger to heat air by carrying out heat exchange between the air and hot water (engine coolant). The heat emitted from the electric heat emitter radiates to the air through corrugated fins of the heat exchanger. Such a configuration simplifies a heat radiating mechanism of the electric heat emitter. Further, the pressure loss of the air flowing in a heating unit casing that is typically caused by an independent electric heat emitter is decreased.
However, according to the above conventional heat exchanger, the ground side electrode of the electric heat emitter is connected to a metal tube through which the hot water flows, and which supports the electric heat emitter. The tube is connected to a vehicle body through the heat exchanger to ground. Therefore, when an electric current is supplied to the electric heat emitter, the electric current flows through the metal tube. The metal tube tends to corrode because the inside of the tube contacts the hot water. Accordingly, the heat emitter current flowing through the metal tube tends to electrically corrode the tube causing the corroded part to leak water.